Income per Common Share of the Trust (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	850,000	1,641,000	905,000	1,219,000
Stock Issued During Period, Shares, Stock Options Exercised	77,000		588,000		256,000
Income per Common Share of the Trust [Abstract]
Income from continuing operations net of noncontrolling interest	$ 29,635	$ 30,021	$ 93,689	$ 88,537
Weighted Average Number of Shares Outstanding, Basic	117,141,000	115,014,000	116,625,000	114,547,000
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.26	$ 0.26	$ 0.80	$ 0.77
Dilutive shares for long-term compensation plans	902,000	766,000	837,000	782,000
Weighted Average Number of Shares Outstanding, Diluted	118,043,000	115,780,000	117,462,000	115,329,000
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.26	$ 0.26	$ 0.79	$ 0.76
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(1,829)	5,299	5,317	60,670
(Loss) income from Discontinued Operations, Net of Tax, Per Basic Share	$ (0.02)	$ 0.05	$ 0.05	$ 0.53
Discontinued operations net of noncontrolling interest, Per Diluted Share	$ (0.02)	$ 0.05	$ 0.05	$ 0.53
Net Income (Loss) Available to Common Stockholders, Basic	$ 27,806	$ 35,320	$ 99,006	$ 149,207
Earnings Per Share, Basic	$ 0.24	$ 0.31	$ 0.85	$ 1.30
Earnings Per Share, Diluted	$ 0.24	$ 0.31	$ 0.84	$ 1.29